Methods of exposure for the purpose of thermal management for imprint lithography processes

ABSTRACT

The present invention is directed to a method that attenuates, if not avoids, heating of a substrate undergoing imprint lithography process and the deleterious effects associated therewith. To that end, the present invention includes a method of patterning a field of a substrate with a polymeric material that solidifies in response to actinic energy in which a sub-portion of the field is exposed sufficient to cure the polymeric material is said sub-portion followed by a blanket exposure of all of the polymeric material associated with the entire field to cure/solidify the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationNo. 60/632,125, filed on Dec. 1, 2004, entitled “Methods of Exposure forthe Purpose of Thermal Management for Imprint Lithography Processes,”listing Sidlgata V. Sreenivasan and Byung-Jin Choi as inventors, theentirety of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The United States government has a paid-up license in this invention andthe right in limited circumstance to require the patent owner to licenseother on reasonable terms as provided by the terms of 70NANB4H3012awarded by National Institute of Standards (NIST) ATP Award.

BACKGROUND OF THE INVENTION

The field of the invention relates generally to nano-fabrication ofstructures. More particularly, the present invention is directed to atechnique to achieve overlay alignment of patterns formed duringnano-scale fabrication.

Nano-fabrication involves the fabrication of very small structures,e.g., having features on the order of nano-meters or smaller. One areain which nano-fabrication has had a sizeable impact is in the processingof integrated circuits. As the semiconductor processing industrycontinues to strive for larger production yields while increasing thecircuits per unit area formed on a substrate, nano-fabrication becomesincreasingly important. Nano-fabrication provides greater processcontrol while allowing increased reduction of the minimum featuredimension of the structures formed. Other areas of development in whichnano-fabrication has been employed include biotechnology, opticaltechnology, mechanical systems and the like.

An exemplary nano-fabrication technique is commonly referred to asimprint lithography. Exemplary imprint lithography processes aredescribed in detail in numerous publications, such as United Statespatent application publication 2004/0065976 filed as U.S. patentapplication Ser. No. 10/264,960, entitled, “Method and a Mold to ArrangeFeatures on a Substrate to Replicate Features having Minimal DimensionalVariability”; United States patent application publication 2004/0065252filed as U.S. patent application Ser. No. 10/264,926, entitled “Methodof Forming a Layer on a Substrate to Facilitate Fabrication of MetrologyStandards”; and U.S. Pat. No. 6,936,194, entitled “Functional PatterningMaterial for Imprint Lithography Processes,” all of which are assignedto the assignee of the present invention.

The fundamental imprint lithography technique disclosed in each of theaforementioned United States patent application publications and UnitedStates patent includes formation of a relief pattern in a polymerizablelayer and transferring a pattern corresponding to the relief patterninto an underlying substrate. The substrate may be positioned upon amotion stage to obtain a desired position to facilitate patterningthereof. To that end, a template is employed spaced-apart from thesubstrate with a formable liquid present between the template and thesubstrate. The liquid is solidified to form a solidified layer that hasa pattern recorded therein that is conforming to a shape of the surfaceof the template in contact with the liquid. The template is thenseparated from the solidified layer such that the template and thesubstrate are spaced-apart. The substrate and the solidified layer arethen subjected to processes to transfer, into the substrate, a reliefimage that corresponds to the pattern in the solidified layer.

A need exists, therefore, to provide improved alignment techniques forimprint lithographic processes.

SUMMARY OF THE INVENTION

The present invention is directed to a method that attenuates, if notavoids, heating of a substrate undergoing imprint lithography processand the deleterious effects associated therewith. To that end, thepresent invention includes a method of patterning a field of a substratewith a polymeric material that solidifies in response to actinic energyin which a sub-portion of the field is exposed sufficient to cure thepolymeric material in said sub-portion followed by a blanket exposure ofall of the polymeric material associated with the entire field tocure/solidify the same. These and other embodiments are discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified plan view of an imprint lithography system havinga mold spaced-apart from a substrate;

FIG. 2 is a cross-sectional view of a patterned substrate having aplurality of layers disposed thereon with a mold, shown in FIG. 1, insuperimposition therewith;

FIG. 3 is a simplified side view of a portion of the system shown inFIG. 1, with the mold in contact with a polymeric layer on thesubstrate;

FIG. 4 is a top-down view of a portion of the substrate shown in FIG. 1,the substrate having a plurality of regions associated therewith;

FIGS. 5 and 6 are side views of portions of the mold and the polymericlayer, shown in FIG. 3, with a portion of the polymeric layer solidifiedand/or cross-linked;

FIG. 7 is a top down view of a polymeric material positioned on thesubstrate, shown in FIG. 1, with an outer region of the polymericmaterial being solidified and/or cross-linked;

FIG. 8 is a top down view of a polymeric material positioned on thesubstrate, shown in FIG. 1, with a grating region of the polymericmaterial being solidified and/or cross-linked;

FIG. 9 is a top down view of a polymeric material positioned on thesubstrate, shown in FIG. 1, with isolated regions of the polymericmaterial being solidified and/or cross-linked; and

FIG. 10 is a top down view of a polymeric material positioned on thesubstrate, shown in FIG. 1, with a scanning beam exposing portions ofthe polymeric material.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a system 8 to form a relief pattern on a substrate12 includes a stage 10 upon which substrate 12 is supported and atemplate 14, having a mold 16 with a patterning surface 18 thereon. In afurther embodiment, substrate 12 may be coupled to a substrate chuck(not shown), the substrate chuck (not shown) being any chuck including,but not limited to, vacuum and electromagnetic.

Template 14 and/or mold 16 may be formed from such materials includingbut not limited to, fused-silica, quartz, silicon, organic polymers,siloxane polymers, borosilicate glass, fluorocarbon polymers, metal, andhardened sapphire. As shown, patterning surface 18 comprises featuresdefined by a plurality of spaced-apart recesses 17 and protrusions 19.However, in a further embodiment, patterning surface 18 may besubstantially smooth and/or planar. Patterning surface 18 may define anoriginal pattern that forms the basis of a pattern to be formed onsubstrate 12.

Template 14 may be coupled to an imprint head 20 to facilitate movementof template 14, and therefore, mold 16. In a further embodiment,template 14 may be coupled to a template chuck (not shown), the templatechuck (not shown) being any chuck including, but not limited to, vacuumand electromagnetic. A fluid dispense system 22 is coupled to beselectively placed in fluid communication with substrate 12 so as todeposit polymeric material 24 thereon. It should be understood thatpolymeric material 24 may be deposited using any known technique, e.g.,drop dispense, spin-coating, dip coating, chemical vapor deposition(CVD), physical vapor deposition (PVD), and the like.

A source 26 of energy 28 is coupled to direct energy 28 along a path 30.Imprint head 20 and stage 10 are configured to arrange mold 16 andsubstrate 12, respectively, to be in superimposition and disposed inpath 30. Either imprint head 20, stage 10, or both vary a distancebetween mold 16 and substrate 12 to define a desired volume therebetweenthat is filled by polymeric material 24.

Typically, polymeric material 24 is disposed upon substrate 12 beforethe desired volume is defined between mold 16 and substrate 12. However,polymeric material 24 may fill the volume after the desired volume hasbeen obtained. After the desired volume is filled with polymericmaterial 24, source 26 produces energy 28, e.g., broadband ultravioletradiation that causes polymeric material 24 to solidify and/orcross-link conforming to the shape of a surface 25 of substrate 12 andpatterning surface 18. Control of this process is regulated by processor32 that is in data communication with stage 10, imprint head 20, fluiddispense system 22, source 26, operating on a computer readable programstored in memory 34.

To allow energy 28 to impinge upon polymeric material 24, it is desiredthat mold 16 be substantially transparent to the wavelength of energy 28so that the same may propagate therethrough. Additionally, to maximize aflux of energy 28 propagating through mold 16, energy 28 may have asufficient cross-section to cover the entire area of mold 16 with noobstructions being present in path 30.

Referring to FIGS. 1 and 2, often a pattern generated by mold 16 isdisposed upon a substrate 112 in which a preexisting pattern in present.To that end, a primer layer 36 is typically deposited upon patternedfeatures, shown as recesses 38 and protrusions 40, formed into substrate112 to provide a smooth, if not planar, surface 42 upon which to form apatterned imprint layer (not shown) from polymeric material 24 disposedupon surface 42. To that end, mold 16 and substrate 112 includealignment marks, which may include sub-portions of the patternedfeatures. For example, mold 16 may have alignment marks, referred to asmold alignment marks, which are defined by features 44 and 46. Substrate112 may include alignment marks, referred to as substrate alignmentmarks, which are defined by features 48 and 50.

To ensure proper alignment between the pattern on substrate 112 with thepattern generated by mold 16, it is desired to ensure proper alignmentbetween the mold and substrate alignment marks. This has typically beenachieved employing the aided eye, e.g., an alignment system 53selectively placed in optical communication with both mold 16 andsubstrate 12, concurrently. Exemplary alignment systems have includedocular microscopes or other imaging systems. Alignment system 53typically obtains information parallel to path 30. Alignment is thenachieved manually by an operator or automatically using a vision system.

Referring to FIG. 1, as mentioned above, source 26 produces energy 28that causes polymeric material 24 to solidify and/or cross-linkconforming to the shape of surface 25 of substrate 12 and patterningsurface 18. To that end, often it is desired to complete solidificationand/or cross-linking of polymeric material 24 prior to separation ofmold 16 from polymeric material 24. A time required to completesolidification and/or cross-linking of polymeric material 24 may dependupon, inter alia, a magnitude of energy 28 impinging upon polymericmaterial 24 and chemical and/or optical properties of polymeric material24 and/or substrate 12. To that end, in the absence of any amplifyingagents, i.e., chemically-amplified photoresist of optical lithographyprogresses, the magnitude of energy 28 required to solidify and/orcross-link polymeric material 24 may be substantially greater in imprintlithography processes as compared to optical lithography processes. As aresult, during solidification and cross-linking of polymeric material24, energy 28 may impinge upon substrate 12, template 14, and mold 16,and thus, heat substrate 12, template 14, and mold 16. A substantiallyuniform magnitude of energy 28 may result in substantially uniformheating of substrate 12, template 14, and mold 16. However, adifferential magnitude of energy 28 and/or a differential CTE(coefficient of thermal expansion) associated with substrate 12,template 14, and mold 16 may result in misalignment between substrate 12and mold 16 during solidification and/or cross-linking of polymericmaterial 24, which may be undesirable. To that end, a method tominimize, if not prevent, thermal effects upon substrate 12, template14, and mold 16 is described below.

Referring to FIG. 3, a portion of system 8 is shown. More specifically,patterning surface 18 of mold 16 is shown in contact with polymericlayer 24. Exposure of an entirety of surface 25 of substrate 12 toenergy 28 may increase a temperature thereof, and thus, a linearlyincrease in size of substrate 12, which may be undesirable. To that end,a portion of substrate 12 may be exposed to energy 28, described below.

Referring to FIG. 4, a portion of substrate 12 is shown having aplurality of regions a-p. As shown, substrate 12 comprises sixteenregions; however, substrate 12 may comprise any number of regions. Tothat end, to minimize, if not prevent, the aforementioned linearlyincrease in size of substrate 12, a subset of the regions a-p ofsubstrate 12 may be exposed to energy 28, shown in FIG. 1. Morespecifically, regions f, g, j, and k of substrate 12 may be exposed toenergy 28, with regions a-d, e, h, i, and l-p of substrate 12 beingsubstantially absent of exposure to energy 28. As a result, region a-d,e, h, i, and l-p of substrate 12 may minimize, if not prevent, region f,g, j, and k of substrate 12 from linearly increasing in size, i.e.,region a-d, e, h, i, and l-p of substrate 12 may act as a physicalconstraint to prevent region f, g, j, and k of substrate 12 fromincreasing in size. Regions f, g, j, and k of substrate 12 may each beexposed to energy 28 sequentially or concurrently.

To that end, after exposure of regions f, g, j, and k of substrate 12 toenergy 28, in a first embodiment, regions a-d, e, h, i, and l-p ofsubstrate 12 may be exposed to energy 28 to solidify and/or cross-linkthe same. In a further embodiment, after exposure of regions f, g, j,and k of substrate 12 to energy 28, all regions (a-p) of substrate 12may be exposed to energy 28, i.e., a blanket exposure to completesolidification and/or cross-linking of polymeric material 24.

Referring to FIG. 3, in a further embodiment, it may be desired toexpose a portion of substrate 12, and therefore, polymeric material 24,to energy 28 such that a position between substrate 12 and mold 16 priorto exposure to energy 28 is substantially the same as a position betweensubstrate 12 and mold 16 subsequent to exposure of energy 28. Morespecifically, an interface between substrate 12 and mold 16 viapolymeric material 24 may be maintained before and after exposure ofsubstrate 12, mold 16, and polymeric material 24 to energy 28. As aresult, an increase in size of substrate 12, template 14, and mold 16resulting from thermal-induced scaling may be minimized, if notprevented.

Referring to FIGS. 3, 5, and 6, in a first example of theabove-mentioned, an outer portion 62 of polymeric material 24 may beexposed to energy 28 prior to inner portion 64 of polymeric material 24,with outer portion 62 of polymeric material 24 being solidified and/orcross-linked in response to energy 28. As a result, outer portion 62 maymaintain an interface between substrate 12 and mold 18, and thus,minimize, if not prevent substrate 12 from increasing in size, asdesired. In a further embodiment, after exposure of outer portion 62 ofpolymeric material 24 to energy 28, inner portion 64 of polymericmaterial 24 may be subsequently exposed to energy 28 to solidify and/orcross-link the same. In still a further embodiment, after exposure ofouter portion 62 of polymeric material 24 to energy 28, inner and outerportions 62 and 64 of polymeric material 24 may be exposed to energy 28,i.e., a blanket exposure to complete solidification and/or cross-linkingof polymeric material 24.

Referring to FIGS. 7-9, further examples are shown of exposing desiredregions of polymeric material 24 to minimize, if not prevent, substrate12 from increasing in size, as desired. FIG. 7 shows an outer region 66being exposed to energy 28, shown in FIG. 1, prior to inner region 68being exposed to energy 28, shown in FIG. 1. FIG. 8 shows a grating typeexposure of polymeric material 24, with region 70 being exposed toenergy 28, shown in FIG. 1, prior to regions 72 being exposed to energy28, shown in FIG. 1. FIG. 9 shows an isolated region exposure ofpolymeric material 24, with regions 76 being exposed to energy 28, shownin FIG. 1, prior to region 7 is exposed to energy 28, shown in FIG. 1.

Referring to FIG. 1, energy 28 may have a cross-sectional areaassociated therewith that may be greater in dimension that a desiredregion that is to be exposed to energy 28, i.e. a region a-p ofsubstrate 12, as shown in FIG. 4. To that end, to expose desired regionsof substrate 12 to energy 28, a mask (not shown) may be positionedwithin path 30 such that energy 28 may propagate therethrough andcomprise dimensions commensurate with said desired regions of substrate12 to expose the same to energy 28. Further, the mask (not shown) may beremoved from path 30 such that substantially all regions of substrate 12are exposed to energy 28. In a further embodiment, analogous to theabove-mentioned, a first mask (not shown) may be positioned within path30 such that energy 28 may propagate therethrough to expose a firstsubset of substrate 12; and a second mask (not shown) may be positionedwithin path 30 such that energy 28 may propagate therethrough to exposea second subset of substrate 12.

Furthermore, as described with respect to FIG. 4, a desired subset ofthe plurality of regions a-p of substrate 12 may be processed tominimize, if not prevent, linearly increasing a size of substrate 12[hereinafter small field]. However, the above-mentioned methods may beapplicable to imprinting of large substrates, i.e., whole waferimprinting or display substrate imprinting [hereinafter large field].More specifically, an overlay error associated with large fields may begreater that that as compared to an overlay error associated with smallfields; however, an error tolerance associated with the large fields maybe comparable or less than that associated with the small fields. In anexample of minimizing a size increase of substrate 12 employingimprinting of large substrates, substrate 12 and polymeric material 24may be exposed to energy 28, shown in FIG. 1, employing a multi-ringtype exposure to maintain a desired position between substrate 12 andmold 16, similar to that as mentioned above with respect to FIGS. 3, 5,and 6. Portions of substrate 12 not previously exposed to energy 28,shown in FIG. 1, may be subsequently exposed to energy 28 to completesolidification and/or cross-linking of polymeric material 24.

In a further embodiment, energy 28 may comprise a scanning beam, asshown in FIG. 10, such that desired regions of substrate 12 may beexposed to energy 28. As shown, region 78 of substrate 12 is exposed toenergy 28 prior to region 80 of substrate 12 is exposed to energy 28. Instill a further embodiment, contact between mold 16, shown in FIG. 1,and polymeric material 24 and a path of the scanning beam may bothtravel across substrate 12 and polymeric material 28 in substantiallythe same direction.

Referring to FIG. 1, in still a further embodiment, as mentioned abovesubstrate 12 may be coupled to a substrate chuck (not shown). To thatend, were the substrate chuck (not shown) able to absorb energy 28, itmay be desired to expose substrate 12 and polymeric material 24 toenergy 24 having a reduced magnitude for a longer period of time ascompared to the methods mentioned above. As a result, a thermalvariation of substrate 12 may be minimized, if not prevented, asdesired.

The embodiments of the present invention described above are exemplary.Many changes and modifications may be made to the disclosure recitedabove, while remaining within the scope of the invention. Therefore, thescope of the invention should not be limited by the above description,but instead should be determined with reference to the appended claimsalong with their full scope of equivalents.

1. A method of patterning a field of a substrate with a polymericmaterial that solidifies in response to actinic energy: exposing asub-portion of said field to said actinic energy; and exposing all ofsaid field to said actinic radiation, whereby overlay misalignment dueto heating of said substrate by said actinic radiation is reduced. 2.The method as recited in claim 1 wherein exposing all further includesexposing, concurrently, all of said field to said actinic radiation. 3.The method as recited in claim 1 wherein said substrate is asemiconductor wafer and said field is coextensive with an entire area ofone side of said wafer.
 4. The method as recited in claim 1 wherein saidsubstrate is a semiconductor wafer and said field is a sub-part of anentire area of one side of said wafer.
 5. The method as recited in claim1 wherein exposing said sub-portion further includes propagating a fluxof said actinic radiation along a path, with said flux having across-section that is greater in dimensions than said sub-portion andfurther including placing a spatial filter in said path to reduce saidflux, impinging upon said region, to dimensions commensurate with saidsub-portion.
 6. The method as recited in claim 1 wherein exposing saidsub-portion further includes propagating a flux of said actinicradiation along a path, with said flux having a cross-section that isgreater in dimensions than said sub-portion and further includingplacing a spatial filter in said path to reduce said flux, impingingupon said region, to dimensions commensurate with said sub-portion, withexposing all of said field further including removing said spatialfilter from said path.
 7. The method of claim 1 further includingtransferring thermal energy, accumulating in said substrate, away fromsaid substrate by placing said substrate in thermal communication with asupport.
 8. A method of patterning a field of a substrate with apolymeric material that solidifies in response to actinic energy:exposing a first sub-portion of said field to said actinic energy; andexposing a second sub-portion of said field to said actinic radiation,with regions of said field associated with said first sub-portiondiffering from the regions of said field associated with saidsecond-sub-portion to reduce overlay misalignment due to heating of saidsubstrate by said actinic radiation.
 9. The method as recited in claim 8further including establishing said first and second sub-portions sothat aggregate dimensions thereof are coextensive with said field. 10.The method as recited in claim 8 wherein said substrate is asemiconductor wafer and said field is coextensive with an entire area ofone side of said wafer.
 11. The method as recited in claim 8 whereinsaid substrate is a semiconductor wafer and said field is a sub-part ofan entire area of one side of said wafer.
 12. The method as recited inclaim 8 further including establishing said first and secondsub-portions so that aggregate dimensions thereof are coextensive withsaid field, propagating a flux of said actinic radiation along a path,with said flux having a cross-section that is greater than said field,wherein exposing said first sub-portion further includes placing a firstspatial filter in said path to reduce said flux, impinging upon saidregion, to dimensions commensurate with said first sub-portion andexposing said second sub-portion further includes placing a secondspatial filter in said path to reduce said flux, impinging upon saidregion, to dimensions commensurate with said second sub-portion.
 13. Themethod as recited in claim 8 further including establishing said firstand second sub-portions so that aggregate dimensions thereof arecoextensive with said field, propagating a flux of said actinicradiation along a path, with said flux having a cross-section that iscoextensive with said field, wherein exposing said first sub-portionfurther includes placing a first spatial filter in said path to reducesaid flux, impinging upon said region, to dimensions commensurate withsaid first sub-portion and exposing said second sub-portion furtherincludes placing a second spatial filter in said path to reduce saidflux, impinging upon said region, to dimensions commensurate with saidsecond sub-portion.
 14. The method of claim 8 further includingtransferring thermal energy, accumulating in said substrate, away fromsaid substrate by placing said substrate in thermal communication with asupport.
 15. A method of patterning a field of a substrate with apolymeric material that solidifies in response to actinic energy:sequentially exposing a sub-portion of a plurality of sub-portions ofsaid field to said actinic energy until an entire area of said field hasbeen exposed to said actinic radiation, whereby overlay misalignment dueto heating of said substrate by said actinic radiation is reduced. 16.The method as recited in claim 15 wherein each of said plurality ofsub-portions include a plurality of sub-regions, with the sequentiallyexposing further including sequentially exposing said plurality ofsub-regions to said actinic radiation.
 17. The method as recited inclaim 15 wherein said plurality of said sub-portions are exposed toactinic radiation concurrently.
 18. The method of claim 15 furtherincluding transferring thermal energy, accumulating in said substrate,away from said substrate by placing said substrate in thermalcommunication with a support.